Wireless sensor networking is an emerging technology that promises an unprecedented ability to monitor the physical environment using a network of relatively inexpensive sensor nodes that can sense the physical environment in a variety of modalities including temperature, pressure, chemical concentration, motion, etc. Sensor networks may consist of a large number of sensor nodes with communication, sensing, and computation capabilities. Because the wireless sensor nodes are typically battery powered, the sensor nodes may be severely constrained relative to their energy supply. Existing approaches to data collection and information extraction from the wireless sensor nodes rely on in-network processing that requires information routing and coordination between sensor nodes. Multiple hops between sensor nodes may be required to reach a remote destination where the data is to be processed. Thus, in-network processing of collected data from the wireless sensor nodes typically requires significantly more energy than the sensing or computation processing. Additionally, each sensor node may require additional computational capability in order to form an ad-hoc network. As a result, there is a delay associated with receipt of the information as it propagates through the network from node-to-node and potentially additional energy consumption requirements as sensor nodes propagate the information sensed by other sensor nodes.
The location of the phenomena being sensed may be critical to many sensor network applications as well. As a result, the data transmitted between sensor nodes in typical sensor networks includes the location of the originating sensor node. The absolute location of the sensor node may not be known, however, necessitating use of a positioning technology such as inclusion of a global positioning system (GPS) receiver at each sensor node. GPS receivers are vulnerable to jamming and to attenuation. Additionally, the inclusion of a GPS receiver at each sensor node increases the cost of each sensor node. Thus, what is needed is a system that supports information retrieval from the sensor nodes in a more cost effective manner. What is additionally needed is a system that supports receipt of the sensed data with reduced latency and with improved energy efficiency.